1. Field of the Invention
The present invention relates to a photographic film cassette, and more particularly to a film cassette having a cassette shell that is molded from a resin.
2. Description Relative to the Prior Art
A film cassette is constituted by a cassette shell, a spool contained in the cassette shell and photographic film wound around the spool. The used film cassette is unloaded from a camera and forwarded to a photolaboratory, where the exposed film is removed from the cassette shell and developed. The cassette shell is then thrown away.
It is known to provide a film cassette with a film leader that does not protrude from the cassette shell prior to loading and which is thus easily loaded into a camera. Rotation of the spool in the direction of unwinding the film by means of the camera's film feeding mechanism causes the film leader to emerge outside of the cassette through a film passageway. Film cassettes of this type are disclosed in U.S. Pat. Nos. 4,832,275, 4,834,306 and 4,846,418. A cassette shell used for such a film cassette requires a construction provided with annular ridges for contact with the outermost turn of the film wound in a roll in order to prevent the film from loosening and a separating claw for separating the film leader from the outermost turns of the film. The cost for manufacturing such a construction can be reduced by molding the cassette shell from resin as described in Japanese Patent Laid-open Publication Nos. 50-33831 and 57-190948 so as to form the annular ridges and the separating claw integrally with the cassette shell.
General resin products are scarcely susceptible to natural decomposition, so they must be subjected to treatment as industrial waste in order to dispose of them. Film cassettes made of resin constitute a problem because of the very high cost of treatment for disposal of the cassettes, particularly in view of the great number of film cassettes that are constantly consumed. Film cassettes having a resin cassette shell made of a material that is soluble in water or is susceptible of microbial degradation have been proposed, as described in Japanese Patent Laid-open Publication No. 1-102458 and a Japanese patent application filed by the present applicant.
Although it is an advantage, from the standpoint of treatment for disposal, to make cassette shells from a material that is soluble in water or is susceptible of microbial degradation, such cassette shells nonetheless represent a great waste of resources because the material from which they are made is incapable of being recycled.
If a general resin of a low decomposability is molded into a cassette shell, withdrawn and fused for its reuse, there will be problems due to the deterioration of purity of the resin. This is because the resin is mixed with ink, labels and adhesive agents even when subjected to a newly fusing treatment. The surface of the cassette shell is provided with a label adhered thereto providing an indication of the film type, manufacturer and the like. The labels are not easily removable from the cassette shell. On account of a deterioration in the purity of the resin, a change in fluidity of the resin to be melted gives rise to several problems, such as, failure in injection molding of the cassette shell and low intensity of the recycled resin of cassette shell.